The LLVM build system is designed to facilitate the building of third party
projects that use LLVM header files, libraries, and tools. In order to use
these facilities, a Makefile from a project must do the following things:

Set make variables. There are several variables that a Makefile needs
to set to use the LLVM build system:

PROJECT_NAME - The name by which your project is known.

LLVM_SRC_ROOT - The root of the LLVM source tree.

LLVM_OBJ_ROOT - The root of the LLVM object tree.

PROJ_SRC_ROOT - The root of the project’s source tree.

PROJ_OBJ_ROOT - The root of the project’s object tree.

PROJ_INSTALL_ROOT - The root installation directory.

LEVEL - The relative path from the current directory to the
project’s root ($PROJ_OBJ_ROOT).

Include Makefile.config from $(LLVM_OBJ_ROOT).

Include Makefile.rules from $(LLVM_SRC_ROOT).

There are two ways that you can set all of these variables:

You can write your own Makefiles which hard-code these values.

You can use the pre-made LLVM sample project. This sample project includes
Makefiles, a configure script that can be used to configure the location
of LLVM, and the ability to support multiple object directories from a single
source directory.

This document assumes that you will base your project on the LLVM sample project
found in llvm/projects/sample. If you want to devise your own build system,
studying the sample project and LLVM Makefiles will probably provide enough
information on how to write your own Makefiles.

Copy the llvm/projects/sample directory to any place of your choosing.
You can place it anywhere you like. Rename the directory to match the name
of your project.

If you downloaded LLVM using Subversion, remove all the directories named
.svn (and all the files therein) from your project’s new source tree.
This will keep Subversion from thinking that your project is inside
llvm/trunk/projects/sample.

Add your source code and Makefiles to your source tree.

If you want your project to be configured with the configure script then
you need to edit autoconf/configure.ac as follows:

AC_INIT - Place the name of your project, its version number and a
contact email address for your project as the arguments to this macro

AC_CONFIG_AUX_DIR - If your project isn’t in the llvm/projects
directory then you might need to adjust this so that it specifies a
relative path to the llvm/autoconf directory.

LLVM_CONFIG_PROJECT - Just leave this alone.

AC_CONFIG_SRCDIR - Specify a path to a file name that identifies your
project; or just leave it at Makefile.common.in.

AC_CONFIG_FILES - Do not change.

AC_CONFIG_MAKEFILE - Use one of these macros for each Makefile that
your project uses. This macro arranges for your makefiles to be copied from
the source directory, unmodified, to the build directory.

After updating autoconf/configure.ac, regenerate the configure script
with these commands. (You must be using Autoconf version 2.59 or later
and your aclocal version should be 1.9 or later.)

% cd autoconf
% ./AutoRegen.sh

Run configure in the directory in which you want to place object code.
Use the following options to tell your project where it can find LLVM:

--with-llvmsrc=<directory>

Tell your project where the LLVM source tree is located.

--with-llvmobj=<directory>

Tell your project where the LLVM object tree is located.

--prefix=<directory>

Tell your project where it should get installed.

That’s it! Now all you have to do is type gmake (or make if you’re on a
GNU/Linux system) in the root of your object directory, and your project should
build.

In order to use the LLVM build system, you will want to organize your source
code so that it can benefit from the build system’s features. Mainly, you want
your source tree layout to look similar to the LLVM source tree layout. The
best way to do this is to just copy the project tree from
llvm/projects/sample and modify it to meet your needs, but you can certainly
add to it if you want.

Underneath your top level directory, you should have the following directories:

lib

This subdirectory should contain all of your library source code. For each
library that you build, you will have one directory in lib that will
contain that library’s source code.

Libraries can be object files, archives, or dynamic libraries. The lib
directory is just a convenient place for libraries as it places them all in
a directory from which they can be linked later.

include

This subdirectory should contain any header files that are global to your
project. By global, we mean that they are used by more than one library or
executable of your project.

By placing your header files in include, they will be found
automatically by the LLVM build system. For example, if you have a file
include/jazz/note.h, then your source files can include it simply with
#include “jazz/note.h”.

tools

This subdirectory should contain all of your source code for executables.
For each program that you build, you will have one directory in tools
that will contain that program’s source code.

test

This subdirectory should contain tests that verify that your code works
correctly. Automated tests are especially useful.

Currently, the LLVM build system provides basic support for tests. The LLVM
system provides the following:

LLVM contains regression tests in llvm/test. These tests are run by the
Lit testing tool. This test procedure uses RUN
lines in the actual test case to determine how to run the test. See the
LLVM Testing Infrastructure Guide for more details.

LLVM contains an optional package called llvm-test, which provides
benchmarks and programs that are known to compile with the Clang front
end. You can use these programs to test your code, gather statistical
information, and compare it to the current LLVM performance statistics.

Currently, there is no way to hook your tests directly into the llvm/test
testing harness. You will simply need to find a way to use the source
provided within that directory on your own.

Typically, you will want to build your lib directory first followed by your
tools directory.

The LLVM build system provides a convenient way to build libraries and
executables. Most of your project Makefiles will only need to define a few
variables. Below is a list of the variables one can set and what they can
do:

This variable is the relative path from this Makefile to the top
directory of your project’s source code. For example, if your source code
is in /tmp/src, then the Makefile in /tmp/src/jump/high
would set LEVEL to "../..".

This variable contains the name of the program that will be built. For
example, to build an executable named sample, TOOLNAME should be set
to sample.

USEDLIBS

This variable holds a space separated list of libraries that should be
linked into the program. These libraries must be libraries that come from
your lib directory. The libraries must be specified without their
lib prefix. For example, to link libsample.a, you would set
USEDLIBS to sample.a.

Note that this works only for statically linked libraries.

LLVMLIBS

This variable holds a space separated list of libraries that should be
linked into the program. These libraries must be LLVM libraries. The
libraries must be specified without their lib prefix. For example, to
link with a driver that performs an IR transformation you might set
LLVMLIBS to this minimal set of libraries LLVMSupport.aLLVMCore.aLLVMBitReader.aLLVMAsmParser.aLLVMAnalysis.aLLVMTransformUtils.aLLVMScalarOpts.aLLVMTarget.a.

Note that this works only for statically linked libraries. LLVM is split
into a large number of static libraries, and the list of libraries you
require may be much longer than the list above. To see a full list of
libraries use: llvm-config--libsall. Using LINK_COMPONENTS as
described below, obviates the need to set LLVMLIBS.

LINK_COMPONENTS

This variable holds a space separated list of components that the LLVM
Makefiles pass to the llvm-config tool to generate a link line for
the program. For example, to link with all LLVM libraries use
LINK_COMPONENTS=all.

LIBS

To link dynamic libraries, add -l<librarybasename> to the LIBS
variable. The LLVM build system will look in the same places for dynamic
libraries as it does for static libraries.

For example, to link libsample.so, you would have the following line in
your Makefile:

LIBS+= -lsample

Note that LIBS must occur in the Makefile after the inclusion of
Makefile.common.

This variable can be used to add options to the C and C++ compiler,
respectively. It is typically used to add options that tell the compiler
the location of additional directories to search for header files.

It is highly suggested that you append to CFLAGS and CPPFLAGS as
opposed to overwriting them. The master Makefiles may already have
useful options in them that you may not want to overwrite.